I had a doctor ask me what I do for a living the other day. When I said I play online poker he asked "Oh, how does that work?" But I wouldn't waste my time explaining cause he's not gonna get it.
The brain is obviously able to handle mass amounts of info and decisions over extended periods of time. Even if stress is involved sports like hockey and tennis are just as intensive mentally and just as stressful. The younger generations know this and live it, older generations just generally can't keep up.
If there is increased chance of stroke playing poker, it comes from poor diet and lack of exercise, and factors such as smoking or not smoking/eating enough weed/hemp.
Whats more likely is that stimulated brains are healthy brains. For most mass tabling will keep their brain witty sharp and plastic. But for those that patternize the game better, perhaps from more experience, they might no longer stimulate their brains at the same level, and their thinking processes might atrophy some.
We can combat this by picking up new tasks. Or by either specializing or generalizing. But because of such plasticity, its doubtful people here have this issue. Most will naturally expand their learning knowledge and skill. Success in this form breeds confidence which becomes a catalyst for the process.
The issue I think players have is they are putting multitasking and stillness at opposite ends of the spectrum. We should be viewing them as skills to be practiced studied and learned. We have outlined in this thread the purpose for meditation as well as the method which is time practice and study.
Another thing to point out is while doing a single task, the issue might not be the tendency to slip towards multitasking, but rather the brains decision to reprimand or supress/control itself. That inner voice that say "did I just read that page?" is the unneeded friction that hinders the mind. Again I think this is what meditation is for. We should not be afraid of or deny the subconscious and its ability to retain information that the consciousness may or may not.
I also suspect that a missed contributor to stroke and heart/brain problems is neck and posture issues. It doesn't take much of a misalignment to create a vast variety of nervous system and cardiovascular problems. Pretty much every ailment in the book can be caused by such issues. Yoga obviously serves this and shouldn't be considered separate from meditation as they are really to be the same thing.
We tend to view these things as ancient and spiritual but really our current culture and daily life just sucks and is counter intuitive.
There is no way I could sit through a 3 hour movie in a theater, I get offended when my peers ask me too